GLOBIN-5-dependent O₂ responses are regulated by PDL- 1/PrBP that targets prenylated soluble guanylate cyclases to dendritic endings

Aerobic animals constantly monitor and adapt to changes in O₂ levels. The molecular mechanisms involved in sensing O₂ are, however, incompletely understood. Previous studies showed that a hexacoordinated globin called GLB-5 tunes the dynamic range of O₂-sensing neurons in natural C. elegans isolates, but is defective in the N2 lab reference strain (McGrath et al., 2009; Persson et al., 2009). GLB-5 enables a sharp behavioral switch when O₂ changes between 21 and 17%. Here, we show that GLB-5 also confers rapid behavioral and cellular recovery from exposure to hypoxia. Hypoxia reconfigures O₂-evoked Ca²⁺ responses in the URX O₂ sensors, and GLB-5 enables rapid recovery of these responses upon re-oxygenation. Forward genetic screens indicate that GLB-5’s effects on O₂ sensing require PDL-1, the C. elegans ortholog of mammalian PrBP/PDE6÷ protein. In mammals, PDE6÷ regulates the traffic and activity of prenylated proteins (Zhang et al., 2004; Norton et al., 2005). PDL-1 promotes localization of GCY-33 and GCY-35, atypical soluble guanylate cyclases that act as O₂ sensors, to the dendritic endings of URX and BAG neurons, where they colocalize with GLB-5. Both GCY-33 and GCY-35 are predicted to be prenylated. Dendritic localization is not essential for GCY-35 to function as an O₂ sensor, but disrupting pdl-1 alters the URX neuron’s O₂ response properties. Functional GLB-5 can restore dendritic localization of GCY-33 in pdl-1 mutants, suggesting GCY-33 and GLB-5 are in a complex. Our data suggest GLB-5 and the soluble guanylate cyclases operate in close proximity to sculpt O₂ responses.